1. Field of the Invention
The present invention relates to an image display apparatus of head mounted type comprising an image displaying means for displaying first and second images to be observed by right and left eyes of a user wearing the image display apparatus and an optical system for forming first and second virtual images of said first and second images displayed on said image displaying means such that said virtual images can be seen by the user.
2. Description of the Preferred Embodiments
In Japanese Patent Application Laid-open Publications Kokai Hei Nos. 3-188777, 4-26289 and 4-168489, there are disclosed image display apparatuses in the form of gogles or spectacles, in which first and second images displayed on first and second liquid crystal display panels, respectively, are projected into right and left eyes of a user by means of an optical system.
Such an apparatus is inherently of a personal use type, and only the user who wears the apparatus can see a virtual image of a relatively large size. Further, the display apparatus can give an impression of a so-called virtual reality, and the user feels that he or she is actually in a virtual space formed by the displayed virtual image. Moreover, a three dimensional image can be easily realized.
The known head mounted type image display apparatus disclosed in the above publication 4-26289 has a function of viewing surroundings even while wearing the apparatus.
In the known image display apparatus of the kind mentioned above, a position of the virtual image in the space as well as a size of the virtual image are fixed. If the position and size of the virtual image could be changed by the user at will, the image display apparatus would have a new function and an enhanced variety. It might be considered that the position and size of the virtual image could be changed by moving the liquid crystal display panel or mirror or lens. However, this might result in the apparatus being large in size, complicated in construction and expensive in cost, because it would be necessary to provide driving mechanisms and spaces for the movement of these parts.
Further, in the known image display apparatuses, not only position and size of the image, but also posture and shape of the image are not changed. Therefore, when the user moves with respect to the virtual image plane or the head of the user is moved or rotated, the virtual image 400 displayed in an image frame 401 is also moved as illustrated in FIG. 19. This might cause a strange or unnatural feeling and the user might be subjected to a bad feeling just like motion-sickness. Moreover, the frame 401 is fixedly determined by size and shape of the liquid crystal display panel and could not be changed.
In the known image display apparatus described in the above mentioned publication 4-168489, there is provided a detector for detecting a position of the apparatus put on the head of the user, and the displayed image is changed in accordance with a detected position. Therefore, a quasi-stereoscopic image can be seen, so that the above mentioned problems could be solved to a limited extent. In order to improve the natural feeling of the three-dimensional display, the frame 401 should not be seen by the user. Therefore, it is necessary to use the optical system having an angle of view larger than 120.degree.. This results in another problem that the apparatus is liable to be large.
It might be considered that the liquid crystal display panel or optical system could be moved mechanically. However, as explained above, this solution would cause other problems wherein the apparatus becomes large in size, complicated in construction and expensive in cost.